Carburetor



June 27, 1967 D M, @R O 3,328,008

CARBURETOR Filed Sept. 23, 1965' v s Sheets-Sheet 1 Q I N v rt \9 m m l|i INVENTOR v DWIGHT] M. GQRDON ATTORNEY F l G. I.

June 27, 1967 GORDON 3,328,008

CARBURETOR Filed Sept. 25, 1 965 s Sheets-Sheet 2 INVENTOR 7 DWIGHT M.GORDON QWMW v ATTORNEY June 27, 1967 D. M. GORDON CARBURETOR 3Sheets-Sheet 5 Filed Sept. 23, 1965 FIG.7.

INVENTOR DWIGHT M. GORDON WA/C ATTORNEY United States Patent C 3,328,008CARBURETQR Dwight Mansell Gordon, Farmington, Mich, assignor to ACEIndustries, Incorporated, New York, N."i., a corporation of New JerseyFiled Sept. 23, 1965, Ser. No. 489,710 9 Claims. (Cl. 2261-43) Thisinvention relates to carburetors for internal combuston engines, and inparticular to multistage, multibarrel carburetors having provision forthe admission of excess air to the intake manifold of the internalcombustion engine during intervals of deceleration.

As is well-known, it is the function of the carburetor of the automotiveinternal combustion engine to supply the proper fuel-air mixture to theintake manifold of the engine according to operating conditions at anygiven time. To this end the carburetor will usually supply a fairly richmixture for curb idle conditions, and a leaner mixture at part-throttlesteady state cruising conditions. The fuel-air ratio may vary fromapproximately 12. to 1 at curb idle to the considerably leaner 15 to 1ratio for steady state cruising.

It is also well-known that in the intake manifold of an internalcombustion engine, gasoline has a tendency to collect or condense on thewalls of the intake manifold and particularly on the lower surfacesthereof where it forms a layer or pool of fuel. This condensed fuel isof only minor importance during normal operation, since it is constantlybeing withdrawn and replenished in a more or less stable fashion.However, upon deceleration when the throttle valve of the carburetor isclosed, the manifold vacuum changes from the normal 12 to 15 inches ofmercury vacuum to as much as 23 inches mercury vacuum. This highervacuum causes the thus collected fuel to flash rapidly into vapors andbecause of the greatly reduced quantity of air entering by Way of thecarburetor, a very rich mixture can be furnished to the individualcylinders for a short interval of time. This very rich mixturefrequently is incompletely burned in the individual cylinders with theresult that unburned hydrocarbons are exhausted by way of the exhaustports and exhaust manifold. These unburned hydrocarbons, of course, arean important constituent of smog. Under certain conditions the unburnedhydrocarbons will ignite in the exhaust manifold resulting in backfire.I have found that with certain modifications to the carburetor structureit is possible to admit additional air to the intake manifold duringdeceleration conditions, whereby a more nearly correct air-fuel mixturecan be supplied to the engine, thus reducing the quantity of unburnedhydrocarbons issuing from the engine and substantially eliminating thetendency of the engine to backfire. Accordingly, it is a primary objectof the invention to provide a new and improved carburetor structurewhich will provide a predetermined optimum mixture of fuel and air tothe engine during the period of deceleration.

It is another object of the invention to provide suitable linkagesbetween the primary throttle shaft and the secondary throttle shaftwhereby the secondary throttle will be opened slightly during a portionof the opening movement of the primary throttle.

It is yet another object of the invention to provide a slow closingmechanism for retarding the closing of the secondary throttle.

These and other objects of the invention will be readily apparent from aperusal of the drawing, the specification and the attached claims.

According to the invention, the primary and secondary throttle shaftsare connected together in such a fashion that the primary shaft willopen a predetermined number of degrees, such as 25 to 30 degrees,without disturbing the position of the secondary throttle. At that timethe further movement of the primary throttle shaft through an additionalrange up to approximately 60 degrees opening of the primary throttle,will progressively open the secondary throttles by a small amount suchas from 5 to 15 degrees from the closed position. Thereafter the normallinkages will take over so that as the primary throttle shaft is movedto its full open position the secondary throttle will also move to itsfull open position so that the two throttles reach the maximum openingat the same time.

There is also provided a slow closing mechanism for the secondarythrottles, so that during deceleration when the primary throttles areabruptly closed, the secondary throttle will remain open for a shortinterval against the bias of the slow closing mechanism. In theinvention as illustrated, the slow closing mechanism takes the form of adashpot operating with liquid in the dashpot, the liquid being the fuelof the carburetor. The delay in closing may range from one to as much assix or seven seconds, depending on circumstances. In an actualcarburetor the delay in closing is of the order of five seconds.

In the drawing,

FIGURE 1 is a top plan view of a carburetor according to the invention.

FIGURE 2 is an end view of the carburetor.

FIGURE 3 is an opposite end view of the carburetor, showing the linkagesconnecting the primary and secondary throttle shafts.

FIGURE 4 shows the operating mechanism of the throttle shafts in anintermediate position.

FIGURE 5 shows the operating mechanism of the throttle shafts in stillanother intermediate position.

FIGURE 6 shows the operating mechanism when the throttles are in fullopen position, and

FIGURE 7 is a simplified schematic of the dashpot actuating mechanism.

Referring to FIGURE 1, there is shown generally at 10 a carburetor ofthe invention. The carburetor 10 is attached by way of bolts 2 to theintake manifold 3 of an internal combustion automotive engine. Thecarburetor is provided with a pair of primary mixture conduits 12 and apair of secondary mixture conduits 14. Mixture conduits such as shownhere are frequentiy called barrels. Each primary mixture conduit orbarrel is provided with a main fuel nozzel cluster 13 for supplying theprimary fuel to the mixture conduit. Also provided but not shown is theidle mixture passage for supplying fuel at curb idle and lowpart-throttle operation.

The secondary mixture conduits are provided With main fuel nozzleclusters 15, although in some carburetors of this general type theventuri is omitted and only a straight fuel nozzle is used.

As is customary, the primary side of the carburetor is provided with achoke plate 16, rotatably mounted on a shaft 18, which by way ofsuitable linkages is controlled by a thermostat indicated generally at20.

Referring to FIGURE 2, it is seen that one end of choke shaft 18 isprovided with a lever arm 22, which is connected by way of link 23 witha fast idle cam 24. The fast idle cam is mounted freely on a pivot 25and is also provided with a stepped portion 26 for adjustment of theidle speed of the engine by way of idle speed adjusting screw 28. Alsomounted on pivot 25 is a secondary throttle lockout 29, which lockoutrotates freely on the pivot. A tab 30 on the fast idle cam movesdownwardly under influence of the thermostatic coil relaxing when theengine warms up and engages a surface 32 on the secondary lockout tomove it out of the locking position.

The secondary throttles are mounted for rotational movement on athrottle shaft 36, which shaft has mounted on it at one end a shortlever arm 38, having a tab 39. The tab 39 is positioned slightly above asurface 34 of the secondary lockout. The purpose of the secondarylockout is to prevent opening of the secondary throttles prior to thetime that the engine is fully warmed up. As shown in FIGURE 2, it isclear that as the choke opens to its full open position, link 23 movesfast idle cam 24 in a clockwise direction, thus rotating tab 30 toengage surface 32, moving the secondary lockout 29 out of the way sothat tab 39 of the secondary throttle can clear the surface 34 of thelookout 29 and permit the secondary throttles to be rotated to anyposition after the engine has fully warmed up.

As shown in FIGURE 2, there is a clearance between the tab 39 and thesurface 34 at the time both primary and secondary throttles are closed.The clearance is equal to approximately to 15 degrees of secondarythrottle rotation and is necessary in the practice of the invention asit will be hereinafter explained.

Also shown in FIGURE 2 is an end of the primary throttle shaft 46, onwhich is mounted an actuating lever arm 48 for connection to anaccelerator pedal not shown. Also mounted on the end of throttle shaft46 is a lever arm 49, upon which is mounted the idle speed adjustingscrew 28 and to which is connected a link 47 for actuating theaccelerator pump of the carburetor.

Referring to FIGURE 3, it is seen that the secondary throttle shaft 36and the primary throttle shaft 46 now occupy the reverse position tothat shown in FIGURE 2. Mounted on and fixed to shaft 46 is a lever arm52, which is provided with a cam surface 54. Arm 52 also has a tab 56which is bent backwardly in the view of FIGURE 3. A coil spring 57 (seeFIGURE 1) has one end hooked over tab 56. Spring 57 encircles the end ofshaft 46 outside the body of the carburetor. A loose lever 60 isprovided with tabs 62 and 64. The other end of coil spring 57 engagesthe lower surface of tab 64. Lever 52 is also provided with a turnedover portion 66, with a curved end which serves as a positive secondarythrottle closing device.

Also mounted on shaft 46 is another loose lever 68, having a surface 70for engagement by tab 64.

Mounted on secondary throttle shaft 36 and fixed thereto is a lever arm72. Arm 72 is provided with an extension 73 upon which is mounted aroller 74 for engagement with cam surface 54, as will be hereinafterexplained. Arm 72 is also provided with a backwardly extending tab 75which when the arm is rotated in the clockwise position comes to restagainst a boss 76, thus limiting the amount the secondary throttles canbe opened. Still another extension of arm 72 is shown at 78, whichextension coacts with the curved surface 66 to serve as a positivecloser for the secondary throttle. A link 79 connects arm 72 with arm68. Still another extension of arm 72, shown at 80, provides means forreceiving an end of link 82. The other end of link 82 connects to aloose lever 84 mounted on a pivot 86.

Also mounted on pivot 86 is an arm 90, having a folded over extension92. The extension 92 is adapted to engage the top of a stem 94 of thedashpot assembly.

The dashpot driving mechanism, as shown in FIG- URES 1 and 3, isillustrated as it would be built for some particular carburetor. Asimplified schematic of the dashpot and driving mechanism is shown inFIGURE 7, where corresponding numerals with the subscript A are used todenote the parts of the mechanism. Thus a link 82A is connected to thelever arm 84A which pivots on a pin 86A. Assuming the arm 84A to therotating in a clockwise direction, a surface 85A presses against anupper surface of a lever arm 90A, also pivoted on pin 86A, and this inturn causes an extension 92A to press upon the stem 94A of the dashpot.Attached to the end of the stern 94A is a piston 96, which is receivedwithin the walls of a cylinder 98. A biasing spring 99 is placed beneaththe piston to urge the piston in an upward direction. The space beneaththe piston communicates by way of a restrictive passageway 101 with thefuel bowl of the carburetor, so that fuel is drawn into the space underthe piston or expelled therefrom, depending upon the direction ofmovement of the piston. The restriction 101 controls the rate at whichthe piston moves.

The operation of the linkages between the two throttle shafts and alsoto the dashpot will now be explained with particular reference toFIGURES 3 through 6. In FIG- URE 3 the throttle shafts, lever arms andlinkages are shown in the throttle closed position. As the primarythrottle is rotated (counterclockwise) lever arm 52 moves downwardlyuntil at the angle shown in FIGURE 4 cam surface 54 just touches roller74. At this point the secondary throttle is still closed. Also, therehas been no movement of the dashpot operating mechanism. Additionalrotation of the primary throttle through the angle shown results in camsurface 54 moving lever arm 72 in a clockwise direction by a few degreesas indicated in FIGURE 5. At this time the primary throttle is openapproximately 60 degrees and the secondary throttle approximately 8 or 9degrees. However, it should be borne in mind that the linkages andlevers can be modified to give a greater or lesser opening of theprimary throttle as well as a greater or lesser opening of the secondarythrottle. Also shown in FIGURE 5 is the downward movement of link 82,which pulls lever 84 in a counterclockwise direction, thus allowinglever to rise and the dashpot piston 96, under the influence of biasingspring 99, moves upwardly to make contact between the stem 94 and theextension 92 of lever 90.

Finally, in FIGURE 6 both secondary and primary throttles have reachedthe fully open position and cam surface 54 has moved completely awayfrom roller 74. Upon closing of the primary throttle, as would happenunder deceleration conditions, the lever arm 52 rotates clockwise andthe extension 66 will rise until it contacts the extension 78 of arm 72,thus forcing the secondary throttle to begin a closing movement. Whenthe throttles have assumed the approximate position of FIGURE 5, thedashpot will begin resisting the closing movement of the secondarythrottles, even though the primary throttle is brought to the fullyclosed position. Under these circumstances, minimum fuel will flow fromthe idle fuel system of the primary barrel and air will be admitted byway of the partially open secondary throttle to lean out the mixture inthe intake manifold of the engine so that more complete combustion ofthe mixture will take place in the cylinders of the engine andbackfiring will be prevented. After a short interval of time eg 1 to 5seconds, the dashpot will have allowed the secondary throttle to come tothe fully closed position and after that time engine operation will benormal.

In a multistage carburetor of the type herein described, the secondarybarrel is intended to supply additional air and fuel for heavy enginedemands. However, in the practice of the invention it is necessary thatwhen the secondary throttles are urged open by the cam surface 54,little or no fuel be supplied by the secondary side. This is easilytaken care of by the calibration of the fuel system in the primarybarrel to supply the addition fuel required when the secondary throttleis cracked open. The fuel system of the secondary side will be adjustedso that fuel will not flow in the secondary main fuel nozzle until thesecondary throttle is opened to some position beyond the openingprovided by the cam surface 54. In this fashion air only will besupplied by the secondary side of the carburetor during decelerationconditions and the leaning out of the air-fuel mixture will beaccomplished in accordance with the object of the invention.

While a liquid dashpot utilizing the fuel of the carburetor has beenillustrated, it will be readily apparent that an air type dashpot,either of the piston type or the diaphragm type, could be utilized inthe practice of the invention. These and other modifications will becomeapparent to one skilled in the art, and it not intended that theinvention be limited beyond'that which is set forth in the appendedclaims.

I claim:

1. Apparatus for reducing the tendency of an internal combustion engineto backfire due to unavoidable enrichment of fuel/ air mixture duringdeceleration conditions, comprising a two stage carburetor adapted to bemounted on an intake manifold, a primary mixture conduit in saidcarburetor for supplying the said combustible mixture at low to moderateloads, a secondary mixture conduit for supplying additional fuel duringperiods of heavy load, and an anti-backfire device comprising means foropening the said secondary throttle approximately to 15 degrees duringmid-range opening of the said primary throttle to admit additional airto the intake manifold without admission of additional fuel and meansincluding a dashpot mechanism operatively coupled to said secondarythrottle to delay closing thereof after said primary throttle has beenclosed for deceleration.

2. The invention of claim 1 in which the said means for openingcomprises a cam on said primary throttle and a cam follower on saidsecondary throttle, the said cam being contoured to move the saidfollower and the said secondary throttle to open the said secondarythrottle by from 5 to 15 while the said primary throttle is movedthrough the range of approximately 25 degrees from closed position toappromixately 65 degrees from closed position.

3. The invention of claim 2 in which the said dashpot comprises a pistonin a cylinder.

4. In an internal combustion engine carburetor having at least oneprimary barrel equipped with a pedal actuated throttle valve and an idlefuel circuit and a main fuel circuit and a secondary barrel providedwith a throttle valve and a main fuel circuit, the improvementcomprising means connecting the secondary throttle shaft to the primarythrottle shaft so as to permit an initial movement of said primary shaftwithout movement of said secondary shaft, means to open said secondarythrottle up to about 15 upon continued movement of said primary shaft,means to open said secondary throttle to its full open position uponcontinued opening of said primary throttle to its full open position andmeans to retard the closing of the said secondary throttle during thefinal closing thereof.

5. The carburetor of claim 4 in which the means to retard closing is adashpot operatively connected to the said secondary throttle shaft.

6. The carburetor of claim 5 in which the said means to open the saidsecondary throttle up to about 15 comprises a cam mounted on saidprimary throttle shaft and a cam follower mounted on said secondarythrottle shaft.

7. The carburetor of claim 6 in which the said cam is so contoured thatit will not engage the said follower until a predetermined opening ofthe said primary throttle has been effected.

8. Apparatus for reducing the tendency of an internal combustion engineto backfire due to unavoidable enrichment of the fuel a-ir mixtureduring deceleration conditions comprising a two stage carburetor havingprimary and secondary mixture conduits, a fuel bowl, an idle fuelcircuit and a main fuel circuit for said primary conduit and a main fuelcircuit for said sec-ondary conduit, a pedal actuated throttle in saidprimary conduit, a secondary throttle in said secondary conduit, meansincluding a connecting link connecting said secondary throttle to saidprimary throttle in such a manner as to allow said primary throttle toopen to about 50 to of its travel before said link picks up the saidsecondary throttle to move the same in such a fashion that the saidsecondary and said primary throttles reach the full open position at thesame time, a cam surface mounted on said primary shaft, a cam followermounted on said secondary shaft, means positioning and arranging saidcam surface and said follower such that the said primary throttle willrotate approximately 20 to35 degrees before contacting the saidfollower, and means including a dashpot operatively linked to saidsecondary throttle in such fashion as to retard the closing thereofduring approximately the final 5 to 15 degrees of closing of the saidsecondary throttle 9. The apparatus of claim 8 in which the said dashpotcomprises a piston in a cylinder and in which the said cylindercommunicates by way of a restriction with the fuel bowl of the saidcarburetor.

References Cited UNITED STATES PATENTS 1,264,126 4/ 1918 Pierce.2,609,807 9/ 2 Winkler. 2,749,100 6/ 1956 Carlson. 2,968,476 1/ 1961Stoltman. 3,006,616 10/1961 Carlson et a1. 3,013,778 12/ 196 1 Carlsonet a1. 3,043,572 7/1962 Ott et al.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Examiner.

4. IN AN INTERNAL COMBUSTION ENGINE CARBURETOR HAVING AT LEAST ONEPRIMARY BARREL EQUIPPED WITH A PEDAL ACTUATED THROTTLE VALVE AND AN IDLEFUEL CIRCUIT AND A MAIN FUEL CIRCUIT AND A SECONDARY BARREL PROVIDEDWITH A THROTTLE VALVE AND A MAIN FUEL CIRCUIT, THE IMPROVEMENTCOMPRISING MEANS CONNECTING THE SECONDARY THROTTLE SHAFT TO THE PRIMARYTHROTTLE SHAFT SO AS TO PERMIT AN INITIAL MOVEMENT OF SAID PRIMARY SHAFTWITHOUT MOVEMENT OF SAID SECONDARY SHAFT, MEANS TO OPEN SAID SECONDARYTHROTTLE UP TO ABOUT 15* UPON CONTINUED MOVEMENT OF SAID PRIMARY SHAFT,MEANS TO OPEN SAID SECONDARY THROTTLE TO ITS FULL OPEN POSITION UPONCONTINUED OPENING OF SAID PRIMARY THROTTLE TO ITS FULL OPEN POSITION ANDMEANS TO RETARD THE CLOSING OF THE SAID SECONDARY THROTTLE DURING THEFINAL CLOSING THEREOF.